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TI-2021-06277 Aliases CVE-2021-23954GHSA-5hq3-8hcw-572m

Type confusion in Mozilla Firefox

Priority MEDIUM 40CWE-843Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
Required
Attack complexity
Low
Impact type
Code execution
Confidentiality · integrity · availability
High · High · High
Fix status
Partial Red Hat: 9 fixed, 1 without a fix

Attack profile from CVSS 3.1 · NVD. Fix status from CNA and Red Hat. Impact type from CWE-843 and the CVSS impact.

Summary

Using the new logical assignment operators in a JavaScript switch statement could have caused a type confusion, leading to a memory corruption and a potentially exploitable crash. This vulnerability affects Firefox < 85, Thunderbird < 78.7, and Firefox ESR < 78.7.

Why it matters now

EPSS 0.01186 68th percentileScored 2026-11-07
Fix Partial Firefox (Mozilla): 85Thunderbird (Mozilla): 78.7+1 more productRed Hat: 8 advisoriesRed Hat: 9 fixed, 1 without a fix

SSVC decision points

Not available: CISA has not published SSVC decision points for this record.

Affected products

VendorProductAffected versionsFixed inStatusSource
MozillaFirefoxbefore 8585Patch availableCNA
MozillaThunderbirdbefore 78.778.7Patch availableCNA
MozillaFirefox ESRbefore 78.778.7Patch availableCNA
  • Firefox VendorMozilla Affected before 85 Fixed in 85 Patch available CNA
  • Thunderbird VendorMozilla Affected before 78.7 Fixed in 78.7 Patch available CNA
  • Firefox ESR VendorMozilla Affected before 78.7 Fixed in 78.7 Patch available CNA

CPE configurations NVD · 3

CPEVersionsRoleVendor
cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*before 85.0VulnerableMozilla
cpe:2.3:a:mozilla:firefox_esr:*:*:*:*:*:*:*:*before 78.7VulnerableMozilla
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*before 78.7VulnerableMozilla
  • cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:* Versions before 85.0 Vulnerable ·Mozilla
  • cpe:2.3:a:mozilla:firefox_esr:*:*:*:*:*:*:*:* Versions before 78.7 Vulnerable ·Mozilla
  • cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:* Versions before 78.7 Vulnerable ·Mozilla

Remediation

  • Fix · CNA Firefox (Mozilla) Fixed in 85
  • Fix · CNA Thunderbird (Mozilla) Fixed in 78.7
  • Fix · CNA Firefox ESR (Mozilla) Fixed in 78.7

Red Hat 8 advisories

  • RHSA-2021:0397 Released 2021-02-03 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream EUS (v. 8.1) thunderbird-78.7.0-1.el8_1
  • RHSA-2021:0298 Released 2021-01-28 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream (v. 8) thunderbird-78.7.0-1.el8_3
  • RHSA-2021:0297 Released 2021-01-28 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux Client (v. 7) thunderbird-78.7.0-1.el7_9
    • Red Hat Enterprise Linux Server Optional (v. 7) thunderbird-78.7.0-1.el7_9
    • Red Hat Enterprise Linux Workstation (v. 7) thunderbird-78.7.0-1.el7_9
Show 5 more Red Hat advisories
  • RHSA-2021:0299 Released 2021-01-28 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream EUS (v. 8.2) thunderbird-78.7.0-1.el8_2
  • RHSA-2021:0290 Released 2021-01-28 · Red Hat rating Important
    firefox security update
    • Red Hat Enterprise Linux Client (v. 7) firefox-78.7.0-2.el7_9
    • Red Hat Enterprise Linux Client Optional (v. 7) firefox-78.7.0-2.el7_9
    • Red Hat Enterprise Linux Server (v. 7) firefox-78.7.0-2.el7_9
    • Red Hat Enterprise Linux Server Optional (v. 7) firefox-78.7.0-2.el7_9
    • Red Hat Enterprise Linux Workstation (v. 7) firefox-78.7.0-2.el7_9
    • Red Hat Enterprise Linux Workstation Optional (v. 7) firefox-78.7.0-2.el7_9
  • RHSA-2021:0288 Released 2021-01-27 · Red Hat rating Important
    firefox security update
    • Red Hat Enterprise Linux AppStream (v. 8) firefox-78.7.0-2.el8_3
  • RHSA-2021:0289 Released 2021-01-27 · Red Hat rating Important
    firefox security update
    • Red Hat Enterprise Linux AppStream EUS (v. 8.2) firefox-78.7.0-2.el8_2
  • RHSA-2021:0285 Released 2021-01-27 · Red Hat rating Important
    firefox security update
    • Red Hat Enterprise Linux AppStream EUS (v. 8.1) firefox-78.7.0-2.el8_1

Vendor assessments

Red Hat

Red Hat rating: Important. Red Hat's page for this CVE →

ProductStatusPlan or fix
Red Hat Enterprise Linux 6AffectedNo fix planned: Out of support scope
Red Hat Enterprise Linux AppStream (v. 8)Fixed RHSA-2021:0288, RHSA-2021:0298
Red Hat Enterprise Linux AppStream EUS (v. 8.1)Fixed RHSA-2021:0285, RHSA-2021:0397
Red Hat Enterprise Linux AppStream EUS (v. 8.2)Fixed RHSA-2021:0289, RHSA-2021:0299
Red Hat Enterprise Linux Client (v. 7)Fixed RHSA-2021:0290, RHSA-2021:0297
Red Hat Enterprise Linux Client Optional (v. 7)Fixed RHSA-2021:0290
Red Hat Enterprise Linux Server (v. 7)Fixed RHSA-2021:0290
Red Hat Enterprise Linux Server Optional (v. 7)Fixed RHSA-2021:0290, RHSA-2021:0297
Red Hat Enterprise Linux Workstation (v. 7)Fixed RHSA-2021:0290, RHSA-2021:0297
Red Hat Enterprise Linux Workstation Optional (v. 7)Fixed RHSA-2021:0290

Timeline

  1. 2026-10-02 Threatist record created from CVE-2021-23954
  2. 2026-10-03 Alias added: GHSA-5hq3-8hcw-572m

References

Advisory 4

  • TI-2024-08981 Use after free in Mozilla Firefox KEVCVSS 3.1CRITICAL 9.8
  • TI-2022-09832 Use after free in Mozilla Firefox KEVCVSS 3.1CRITICAL 9.6
  • TI-2019-08769 Improper input validation in Mozilla Firefox ESR KEVCVSS 3.1CRITICAL 10.0
  • TI-2010-03577 Mozilla Firefox 3.5.x through 3.5.14 and 3.6.x through 3.6.11, Thunderbird 3.1.6 before… KEVCVSS 3.1CRITICAL 9.8
  • TI-2023-04799 Out-of-bounds write in Google Chrome KEVCVSS 3.1HIGH 8.8
  • TI-2023-04477 Out-of-bounds write in Google Chrome KEVCVSS 3.1HIGH 8.8
See all 3444 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences